Objective To compare and evaluate the biocompatibility of three kinds of dentin bonding agents Xeno Ⅲ（XO）, Adper Prompt（AP）, Single bond2（SB）through cell culture in vitro. Methods Three kinds of dentin bonding agents（XO, AP, SB）were applied on the surface of the dental slices which were 5.0 mm in diameter and 0.5 mm in depth. By immersing the slices into the DMEM culture medium, the maceration extracts were obtained. Normal dental pulps of teenagers were collected and human pulp fibroblast was cultured using tissue explant method. The fifth generation pulp cells were exposed to culture medium containing different concentrations of maceration extracts （100.0%, 50.0%, 25.0%, 12.5%） for 24, 72, 120 h. At last, MTT method was used to evaluate the cytotoxicity of the dentin bonding agents on human pulp fibroblast. Results The results showed that all three kinds of dentin bonding systems had cytotoxicity to human pulp fibroblast in different degree in vitro. The cytotoxicity of XO and AP was less than SB. The difference was statistically significant（P
